1. Field of the Invention
The present invention relates to internal combustion engines, and, more particularly, to piston cooling nozzles for cooling pistons in such engines.
2. Description of the Related Art
During operation of an internal combustion (IC) engine, a small percentage of the heat available in the fuel is absorbed by the pistons. While this percentage is only in the 3 to 8 percent range for aluminum alloy pistons, there is still a noticeable rise in the temperature of the pistons due to this heat absorption. While there is some heat transfer away from the pistons and hence some cooling, additional cooling is frequently needed to keep the piston temperature within a target operating temperature range. Heat is transferred via conduction heat transfer from the piston rings, land and skirt portions of the piston to the water jacket and crankcase oil. If higher than desired piston temperatures occur and there is insufficient cooling, the result can be increased crown, top land and top groove carbon deposits. As a general rule, top groove temperatures greater than 220° C. (428° F.) are considered excessive.
Under certain conditions it may be desirable to provide additional cooling of the piston to ensure satisfactory operation. One technique which is used to enable additional cooling by way of oil cooling is to provide a piston cooling nozzle (PCN) in combination with a specific piston design. The PCN has an inlet which receives oil at rifle pressure from the oil rifle in the engine block, and an outlet which directs cooling oil toward the piston resulting in a divergent, non-targeted plume of oil being sprayed onto the underside of the piston. The divergent, non-targeted spray results in some portion of the oil being sprayed against piston surfaces which are not critical and which are not the preferred surfaces for the most effective cooling and heat transfer. When the piston includes an undercrown cooling gallery, the preferred location for the plume of oil is directly into the cooling gallery. However, with a PCN having a divergent, non-targeted spray pattern, only a small portion of the cooling oil is actually sprayed into the gallery.
Another type of PCN provides a nozzle design that creates a targeted oil jet plume which is directed against the piston. With a targeted spray, it is easier to direct the spray to a localized and specific area of the piston such as a piston cooling gallery opening. An example of a targeted PCN is disclosed in U.S. Pat. No. 5,649,505 (Tussing), which is assigned to the assignee of the present invention and incorporated herein by reference.
With PCN designs utilized to date, the PCN orientation is determined by a special interface between the PCN and the engine block to which the PCN is mounted. The engine block is typically cast with an additional locating feature which interfaces with the PCN to properly orient the PCN. Since a casting process is not as accurate as a machining process, the proper orientation of the PCN can vary somewhat relative to the piston cooling gallery opening.
What is needed in the art is a piston cooling nozzle which is configured to be quickly and accurately located relative to an undercrown cooling gallery to ensure proper cooling of the piston.